Mechanical control for submerged hydrofoil systems



Aug. 29, 1967 J. K. ROPER 3,338,202

MECHANICAL CQNTHOL FOR SUBMERGED HYDROFOIL SYSTEMS Filed Aug, 16, 1965 l4 /6 F|G.2 I 29 H64 I #6 286 /5 l4 fixaww jfi 4 Ila I 27 IL //C 19:276 2s 26 FIG.5

INVENTOR.

JOHN K. ROPER A TTORNEYS.

United States Patent Ofifice 3,338,202 Patented Aug. 29, 1967 3,338,202 MECHANICAL CONTROL FOR SUBMERGED HYDROFOIL SYSTEMS John K. Roper, Stony Brook, N.Y., assignor to Atlantic Hydrofoils, Inc., Stony Brook, N.Y., a corporation of New York Filed Aug. 16, 1965, Ser. No. 479,745 5 Claims. (Cl. 114-665) The present invention relates to an automatic, passive, mechanical control system for stabilizing the motions of marine craft which are supported by submerged hydrofoil systems and which are subject to operation under either calm water or wave conditions.

In the operation of hydrofoil marine craft with uncontrolled submerged hydrofoil support systems, it is known that the craft requires some form of height sta- 'bilization control when operating in either smooth water or Waves. In smooth water, uncontrolled submerged hydrofoil systems may develop continuously oscillating, heaving and pitching motions or so-called divergent pitching or heaving motions which may cause the hull of the hydrofoil craft to crash against the water surface. When uncontrolled submerged hydrofoil systems are run in a seaway, the wave disturbing forces can result in extremely uncomfortable heaving and pitching motions of the craft and/or cause the bow of the hull to crash onto on-coming wave flanks. All the above described events can seriously hamper or prevent successful operation of the hydrofoil boat.

In the past, many attempts were made to control the hydrodynamic forces on the submerged hydrofoil by the use of combined electronic and mechanical control systems. These control systems usually sense the disturbance of the craft by continuously monitoring (usually electrically) the accelerations or motions of the craft and then, by mechanical means, provide for effective angle of attack changes on the submerged foils to vary the hydrodynamic disturbing forces on the hydrofoil in order to overcome the Wave disturbances. These electronic-mechanical auto-pilot systems are complex in design, require continuous maintenance, are costly, and could cause a hydrofoil boat to be inoperable if only one of its many components becomes defective.

Savitsky Patent No. 3,092,062, dated June 4, 1963, and my prior Patent No. 3,170,432, dated Feb. 23, 1965, disclose a passive, mechanical, automatically operating simple hydrofoil control system which possesses all the advantages of a submerged hydrofoil system without the complexity, expense, and involved maintenance required of electronic-mechanical auto-pilot systems. As disclosed in these prior patents, a control flap on the submerged hydrofoil is mechanically linked to a vertical trailing edge flap on the vertical strut which supports the submerged hydrofoil to the hull of the craft. The vertical flap pivots about a vertical axis and extends rearwardly and sidewardly of said axis. In smooth Water operation of a marine craft using this prior system, as the hydrofoil boat tends to fall towards the water surface, the vertical flap on the vertical support strut is so arranged as to be deflected about the vertical axis by the hydrodynamic side forces developed by the increased eflective immersion of the flap. Through a suitable linkage system the deflection of the vertical flap causes a deflection of the control flap on the submerged hydrofoil, thus increasing the hydrodynamic lift on the hydrofoil and causing the hydrofoil craft to rise until an equilibrium altitude is attained. At some preselected operating height of the boat, the vertical flap is designed to be clear of the water and the height stabilization is achieved by the natural hydrodynamic phenomena wherein the submerged hydrofoil loses hydrodynamic lift as it approaches the free water surface and gains as its submergence is increased.

In the use of this prior system on marine craft operating in waves, the rising water surface of the wave profile actuates the vertical flap so that its deflection about the vertical axis causes a deflection of the flap of the submerged foil which in turn increases the hydrodynamic lift force on the surmerged hydrofoil so as to raise the hull over the oncoming Wave flank. The distance that said vertical flap extends beyond the side of said strut will of course vary as the vertical flap is deflected. The size of the submerged hydrofoil control flap, the size of the vertical depth control flap on the vertical support strut and the required mechanical linkages between these flaps are arranged and proportioned to provide any desired sensitivity and response characteristics to wave disturbances as to assure a minimum total craft response to the hydrodynamic forces developed by operation in waves.

The present invention functions somewhat analogously to, and has many of the advantages of, this prior system described above, but, as one feature, provides for a passive, mechanical, automatically operating simple hydrofoil control system having an alternate mechanical construction and operation depending upon rearward drag forces rather than side forces. A substantially vertical strut member is connected at its upper end to the hull of a vessel, said strut having a fore-to-aft axis, and a hydrofoil plane is disposed at the lower end of the strut member and is operable to maintain a hydrodynamic lift of the vessel to a minimum submergence of the hydrofoil plane below the free water surface at cruise speed of the vessel. The hydrofoil plane is formed at least in part by a horizontal flap which is pivotal relative to the strut. A' drag means is provided secured to the strut for pivotal movements about a horizontal axis perpendicular to the fore-to-aft axis of the strut, and the drag means extends rearwardly and downwardly of said horizontal axis when the drag means is in its cruise position. The drag means includes at least one drag vane extending outwardly beyond one side of said strut for exposure to water flow, and the distance so extended by the perimeter of the vane remains fixed as the drag means pivots about the horizontal axis. The drag means is interconnected to the horizontal flap by a mechanical linkage so that when unbalanced external forces are applied to either the horizontal flap means or the drag means causing it to pivot, a force is applied to the other interconnected means to pivot said other means toward a position for equalizing the force applied to both said interconnected means. The drag means pivots in a forward-rearward, upward-down- Ward direction, and at the cruise height of the boat, the lower end of the drag vane is designed to be clear of the water. As this height decreases, the drag vane is immersed and the drag means is pivoted aft due to the force of the Water on the surface of the drag vanes to thereby pivot the horizontal flap and increase the lift on said flap until the height of the vessel is restored to its cruise height.

Another feature of the present invention is that the drag principle of operation does not create substantial sideward bending moments on the strut. Such bending moments, found in control systems operating by side forces deflecting a single control flap sidewardly about a vertical axis, exert large forces on the strut at high boat speeds, and structural compensation is therefore required. Such bending moments in said control systems further exert turning moments on the boat which require compensation. The further provision in the present invention of two drag vanes symmetrically extending to opposite sides of the strut fore-to-aft axis outwardly beyond each side of the strut respectively for exposure to water flow, prevents any total sideward bending moments being exerted on the strut and drag means. The

small sideward bending moments equally created by the drag forces on the two drag vanes on each side of the fore-to-aft strut axis are balanced out against each other.

A further feature of the present invention provides for mounting said drag means to said strut in a manner to protect the mounting and to allow an uninterrupted flow of water along the strut to the forward surface of the drag vane br vanes.

An additional feature of the present invention is the provision of drag means which will soften the response of the hydrofoil control system to larger waves and which will tend to disregard small waves of insufilcient height to strike the hull of the boat when it is at cruising speed.

A further feature of the present invention is the provision of drag means which will permit the craft to achieve self-compensating cruise equilibrium and maintain a relatively constant level of the craft above the water at a plurality of distinctly different cruise speeds.

Another feature of the present invention is a drag means which provides acceleration feedback compensation for accelerations of the craft in an upward or downward direction. As the craft accelerates in one of said directions, the opposite reaction of the mass of the drag means causes it to pivot in the opposite direction to vary the lift on the hydrofoil plane to compensate for the acceleration.

Other features and theattendant advantages of the present invention will be readily appreciated by reference to the following description, when considered in connection with the accompanying drawings wherein:

FIGURE 1 is a side view of the present invention illustrating a hydrofoil system which includes drag means positioned on a support strut vertically mounted to a hydrofoil marine craft;

FIGURE 2 is a sectional view on line 2-2 of FIG. 1;

FIGURE 3 is a rear elevational view of one embodiment of the vanes of said drag means;

FIGURE 4 is a rear elevational view illustrating one alternate configuration of the vanes of said drag means;

FIGURE 5 is a rear elevational view illustrating a second alternate configuration of the vanes of said drag means.

Referring now to the drawings, there is shown in FIG- URE 1 a submerged hydrofoil attached to a vertical support strut 11 which is in turn attached at its top portion to the hull of a marine craft 12. Hydrofoil 10 may include ahorizontal control flap 13 at its trailing edge pivotal about strut 11 as shown, or the entire hydrofoil 10 may be pivotal about strut 11. Strut 11 has. fore-to-aft axis 14-14, and 'drag means generally designated as 15 is pivotally connected to strut 11. A mechanical linkage 17 connects horizontal control flap 13 to drag means 15.

Drag means 15 shown in FIGURES 1 and 2 includes two symmetrical vanes 27 and 28 which extend to opposite sides of axis 14-14 outwardly beyond sides 11a and 11b respectively of strut 11. Vanes 27 and 28 are integrally connected to support arm 19 of drag means 15 which in turn is pivotally connected to strut 11 by a pivot 20 passing through said arm 19. Pivot 20 extends along a horizontal axis 1616 perpendicular to the strut fore-toa-ft axis 1414, and drag means 15 is therefore pivotal about said axis 1616 in the manner shown by the arrow in FIGURE 1.

The mechanical linkage connecting horizontal control flap 13 to drag means 15 consists of a push rod 17 which is pivotally mounted at one end 17a to flap 13 and is pivotally mounted at its other end 17b to lever extension 19a of support arm 19. When drag means 15 pivots about axis 1616, extension 19a of support arm 19 pivots and acts through push rod 17 to cause flap 13 to pivot. The deflection rate of drag means 15 may be adjusted to any desired proportion of the deflection rate of flap 13, such as by changing the distance between the end 17b of push rod 17 and pivot 20.

Drag means 15 including vanes 27 and 28 assumes the 4 position shown in FIGURE 1 at the cruise speed of the craft, and the lower ends 27a and 28a of said vanes terminate above the surfaceof the water 21 at said cruise speed. Drag means 15 extends rearwardly and downwardly of horizontal axis 16-16 in this position. At heights of the craft above the water less than cruise speed height, however, vanes 27 and 28 extending outward beyond the sides 11:: and 11b of the strut 11 will be exposed to water flow along the sides of strut 11. The forward surfaces 27b and 28b of vanes 27 and 28 will then act as drag surfaces, and the forces of the water flow against said surfaces will pivot drag means 15 rearwardly and upwardly. As said drag means pivots, the outer perimeter of each vane continues to extend a fixed distance beyond its corresponding side of strut 11. In actual operation of the craft at low speeds, drag means 15 will be immersed in the water and deflected rearwardly and upwardly. Flap 13 of submerged hydrofoil 10 will be deflected downwardly due to the hydrodynamic load on drag means 15. A large hydrodynamic lift force is developed by the large lift coeflicient of hydrofoil 10 and downwardly deflected flap 13, and the boat tends to lift itself out of the water. As the speed of the draft increases, the required lift coeflicient to support the craft is decreased -and the hull of the boat is actually lifted out of the water. The hydrodynamic load on rearwardly deflected vanes 27 and 28 then decreases as their immersion is reduced due to the craft rising. The increased load on submerged flap 13 causes its own deflection to be reduced and in turn, through linkage 17, causes drag means 15 to deflect downwardly and forwardly toward strut ll until an equilibrium moment condition is achieved between the horizontal flap and drag means loads. This process continues,

'i.e., as the craft goes faster, the horizontal flap 13 loads are increased, and the craft n'ses reducing the effectiveness of the drag vanes 27 and 28 until the craft reaches an equilibrium cruise height at which drag means 15 including vanes 27 and 28 is completely out of the water as shown in the FIGURE 1 position. Flap 13 is then no longer deflected, its further upward movement being prevented by a physical upper stop 22.

Further increases in craft height are then controlled by the hydrodynamic phenomena which causes a reduction in hydrofoil lift as the submerged hydrofoil approaches the free water surface. If, for any reason, the craft is caused to move towards the free water surface, vanes 27 and 28 of drag means 15 are actuated by the water flow to pivot rearwardly and cause a downward deflection of flap 13. The hydrodynamic lift force on the hydrofoil increases and the craft is caused to rise again to an equilibrium cruise condition. It will further be noted that the control system is relatively insensitive to the vertical orbital velocities of the particular wave system being operated in.

FIGURES l and 2 illustrate support arm 19, pivot 20, push rod 17 and the end connections of push rod 17 all enclosed within a channel 11c extending forwardly from the rear of strut 11 and defined by side walls and 11b of said strut. The advantage of this enclosed construction is that their elements are protected from damage and fouling, and further, the resultant streamlined side surfaces 11a and 11b of srut 11 allow an uninterrupted flow of water rearwardly along strut 11 to deliver equal forces on forward surfaces 27b and 28b of drag vanes 27 and 28. If arm 19 were pivotally mounted on an outer side surface of strut 11, such as side 11a, and not enclosed, the water flow along that side of the strut would be interrupted by the mounting means and arm 19, sub ject to flow break away around vane 27, and would result in unequal drag forces delivered to vane surfaces 27b and 28b. The flow break away from surface 27b would be erratic, and the unequal forces on said vanes would introduce a bending torque on drag means 15 and strut 11. The flow breakaway would further produce an uneven response of drag means 15. While such as unenclosed side mounting of drag means 15 is within the scope of the present invention, the preferred embodiment is the enclosed mounting described above.

The above description discloses as a preferred embodiment two symmetrical drag vanes 27 and 28 mounted on said support arm 19, but it will be recognized that a less efficient but still adequate embodiment of the present invention comprises only one vane, either 27 or 28, integrally connected to support arm 19. Support arm 19 may be pivotally mounted to strut 11 within channel 110, or may be mounted to a surface side of said strut. Said single vane presents only one forward surface for exposure to water flow, said surface extending outwardly beyond only one side of strut 11, and a small sideward bending moment and turning moment due to the water force on said vane will be introduced on drag means 15 and strut 11.

FIGURE 3 illustrates the rear elevational view of vanes 27 and 28 in their FIGURE 1 position.

FIGURES 4 and 5 illustrate two alternate configurations for said vanes 27 and 28 of FIGURE 3, respectively showing vanes 29, 30 and vanes 31, 32 in rear elevational views directly corresponding to FIGURE 3.

FIGURE 4 shows vanes 29 and 30 symmetrical about axis 1414 and each having an outer edge which converges toward the side of strut 11 as said edge extends toward its lower end. The advantage of this configuration is that when the craft is at cruise speed with said vanes out of the water, short waves of insuflicient height to strike the hull of the boat will only react with the lower, small area portion of said vanes; the response of the craft will be relatively slight, as it should be for waves which do not affect the boat. Higher waves will react with the entire area of the vanes, and the craft will essentially contour and lift over these waves. This tapered configuration of each vane may be linear or curvilinear, and is a means for softening the response of the craft to all waves by allowing said waves to react with the vanes in a smoothly increasing fashion.

FIGURE 5 shows vanes 31 and 32 symmetrical about axis 14-14, wherein each vane is divided into a plurality of distinct sections, each section providing self-compensating control of the hydrodynamic lift of the boat at a distinctly different cruise speed and maintaining the craft at a relatively constant level over the water for each cruise speed. The vane configuration shown, having two sections 25 and 26, allows the craft to cruise at two different speeds varying by several hundred percent while still maintaining self-compensating control. Level 23-23 defines the water level at one cruising speed, and level 24--24 defines the water level at a further cruising speed several times that of the first cruising speed. The difference between these two heights is small compared to the height of each vane. Section 25 is small in area compared to section 26, and has small effect on self-compensating control of the craft at the lower speed. Each section of each vane may take a variety of shapes depending on the response characteristic desired.

Drag means 15 of the present invention, operating as described above to pivot in an upward-downward direction as well as in a forward-rearward direction, further aids in self-compensating control of the craft by applying the principle of acceleration feedback. Whenever the craft for any reason, such as a particular wave system, accelerates in either an upward or a downward direction, the principle of inertia results in drag means 15 accelerating in the opposite direction in relation to strut 11. This opposite acceleration of said drag means in relation to said strut acts through linkage 17 to deflect flap 13 to either increase or decrease the lift of the hydrofoil 10. This varying of the lift acts to counteract the original acceleration of the boat, in addition to the effects of water forces on said drag means, and results in more stable operation of the craft. The amount of acceleration feedback obtained will of course depend upon the mass of drag means 15, and is therefore a variable effect.

While the invention has been disclosed herein in connection with particular embodiments and specific structural details, it is clear that numerous changes and modifications could be made by those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

1. In combination with a water borne vessel, .a passive self-compensating hydrofoil control system comprising a substantially vertical hydrofoil strut member and a hydrofoil plane; said vertical strut member being connected at its upper end to the hull of said vessel and having a foreto-aft axis; said hydrofoil plane being disposed at the lower end of said strut member and operable to maintain a hydrodynamic lift of the vessel to a minimum submergence of the hydrofoil plane below the free water surface at cruise speed of the vessel, said hydrofoil plane being formed at least in part by horizontal flap means pivotable relative to the strut; drag means, including a support member and at least one vane fixedly attached to said support member; means securing said support member to said strut for pivotal movements of said vane and support member about a horizontal axis perpendicular to said fore-to-aft strut axis; said drag means extending rearwardly and downwardly of said horizontal axis in cruise position; said vane extending a fixed distance outwardly beyond at least one side of said strut as said vane pivots about said horizontal axis; said drag means including said vane terminating at its lower end, when said drag means is pivoted to its cruise position, at a height above said hydrofoil plane which is greater than said minimum submergence; and mechanical linkage means interconnecting said horizontal fiap means and said drag means and operable, on application of unbalanced external forces to one of said interconnected means causing it to pivot,

to apply to the other of said interconnected means a force acting to move said other means toward a position for equalizing the forces applied to both said interconnected means.

2. The combination according to claim 1 wherein said drag means includes two symmetrical vanes extending to opposite sides of said strut fore-to-aft axis outwardly beyond each side of said strut respectively.

3. The combination according to claim 1 wherein said drag means is pivotally mounted to said strut within a channel in the trailing edge of said strut.

4. The combination according to claim 1 wherein said vane has an outer edge which converges toward said strut as said edge extends toward its lower end.

5. The combination according to claim 1 wherein said hydrofoil plane is operable to maintain a hydrodynamic lift of the vessel to a plurality of minimum submergences of said plane below the free water surface at a plurality of distinct cruise speeds of the vessel; and, said vane includes a plurality of distinct sections, each said section substantially terminating at its lower end, when said vane is pivoted to its cruise position, at a height above said hydrofoil plane whichis greater than a minimum submergence at a cruise speed.

References Cited UNITED STATES PATENTS 3,170,432 2/ 1965 Roper.

FOREIGN PATENTS 924,374 4/1963 Great Britain.

MILTON BUCHLER, Primary Examiner.

ANDREW H. FARRELL, Examiner. 

1. IN COMBINATION WITH A WATER BORNE VESSEL, A PASSIVE SELF-COMPENSATING HYDROFOIL CONTROL SYSTEM COMPRISING A SUBSTANTIALLY VERTICAL HYDROFOIL STRUT MEMBER AND A HYDROFOIL PLANE; SAID VERTICAL STRUT MEMBER BEING CONNECTED AT ITS UPPER END TO THE HULL OF SAID VESSEL AND HAVING A FORCETO-AFT AXIS; SAID HYDROFOIL PLANE BEING DISPOSED AT THE LOWER END OF SAID STRUT MEMBER AND OPERABLE TO MAINTAIN A HYDRODYNAMIC LIFT OF THE VESSEL TO A MINIMUM SUBMERGENCE OF THE HYDROFOIL PLANE BELOW THE FREE WATER SURFACE AT CRUISE SPEED OF THE VESSEL, SAID HYDROFOIL PLANE BEING FORMED AT LEAST IN PART BY HORIZONTAL FLAP MEANS PIVOATABLE RELATIVE TO THE STRUT; DRAG MEANS, INCLUDING A SUPPORT MEMBER AND AT LEAST ONE VANE FIXEDLY ATTACHED TO SAID SUPPORT MEMBER; MEANS SECURING SAID SUPPORT MEMBER TO SAID STRUT FOR PIVOTAL MOVEMENTS OF SAID VANE AND SUPPORT MEMBER ABOUT A HORIZONTAL AXIS PERPENDICULAR TO SAID FORE-TO-AFT STRUT AXIS; SAID DRAG MEANS EXTENDING REARWARDLY AND DOWNWARDLY OF SAID HORIZONTAL AXIS IN CRUISE POSITION; SAID VANE EXTENDING A FIXED DISTANCE OUTWARDLY BEYOND AT LEAST ONE SIDE OF SAID STRUT AS SAID VANE PIVOTS ABOUT SAID HORIZONTAL AXIS; SAID DRAG MEANS INCLUDING SAID VANE TERMINATING AT ITS LOWER END, WHEN SAID DRAG MEANS IS PIVOTED TO ITS CRUISE POSITION, AT A HEIGHT ABOVE SAID HYDROFOIL PLANE WHICH IS GREATER THAN SAID MINIMUM SUBMERGENCE; AND MECHANICAL LINKAGE MEANS INTERCONNECTING SAID HORIZONTAL FLAP MEANS AND SAID DRAG MEANS AND OPERABLE, ON APPLICATION OF UNBALANCED EXTERNAL FORCES TO ONE OF SAID INTERCONNECTED MEANS CAUSING IT TO PIVOT, TO APPLY TO THE OTHER OF SAID INTERCONNECTED MEANS A FORCE ACTING TO MOVE SAID OTHER MEANS TOWARD A POSITION FOR EQUALIZING THE FORCES APPLIED TO BOTH SAID INTERCONNECTED MEANS. 